The onshore power system which is suitable for environmental protection needs and replaces diesel generators on board is booming. The high temperature rise of modular multilevel rectifier applied to the onshore power system reduces its operating reliability, and the loss is an important parameter to reflect the temperature rise. Ignoring other loss factors of rectifiers, a simplified model is established for the loss of switching devices, and a temperature rise analysis model of modular multilevel converter (MMC) rectifier half-bridge sub-module switching devices is established in combination with the principle of electro-thermal conversion, so as to determine the relationship between temperature rise and switch device loss. Based on the established loss and temperature rise model, the influence of carrier phase shift and nearest level approach modulation on the temperature rise of the switching device is simulated and analyzed, which is consistent with the verification under practical engineering conditions. The results show that the temperature rise of switching devices is smaller under the carrier phase shift modulation mode, and the mode of modulation is able to be used in the actual engineering to suppress the temperature rise to a certain extent. The temperature rise model constructed can provide a model basis for the follow-up study of other temperature rise suppression measures, and can verify the effectiveness of temperature rise suppression measures.